Transparent display device

ABSTRACT

Disclosed is a transparent display device including an electrochromic element. The electrochromic element includes an electrochromic layer, a counter layer, and an electrolyte layer. An image is displayed through an oxidation-reduction reaction, and the display device is in a transparent mode when a voltage is not applied. The electrochromic layer and the counter layer may further include a core material for changing a color at a high speed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No.10-2015-0191487 filed on Dec. 31, 2015, which is hereby incorporated byreference as if fully set forth herein.

BACKGROUND Field of the Invention

The present invention relates to a transparent display device.

Discussion of the Related Art

Recently, as society advances to the information-oriented society, thedisplay field of processing and displaying a massive amount ofinformation is rapidly advancing, and various display devices have beendeveloped and are attracting much attention. The display devices includeliquid crystal display (LCD) devices, plasma display panel (PDP)devices, field emission display (FED) devices, electroluminescencedisplay (ELD) devices, and organic light emitting diode (OLED) displaydevices, etc.

Recently, the display devices are thinned and lightened and are low inconsumption power, and thus, the application field of display devices iscontinuously increasing. Particularly, a display device is used as auser interface in most electronic devices, mobile devices, etc.

Moreover, transparent display devices which enable a user to see abackground or an object disposed on a rear surface thereof are beingactively researched recently.

FIG. 1 is a plan view illustrating a transmissive area (TA) and adisplay area (EA) of a related art transparent display device. In thiscase, the related art transparent display device may be a liquid crystaldisplay device or an organic light emitting display device. The relatedart transparent display device has the following problems.

When the transparent display device is implemented as the liquid crystaldisplay device, it is hard to realize a transmittance of 15% or morebecause of transmittance loss by a polarizing film.

When the transparent display device is implemented as the organic lightemitting display device, securing of the transmissive area is restricteddue to a thin film transistor (TFT), and for example, if the number ofTFTs is reduced, it is hard to realize a high resolution. There is atradeoff relationship between realization of a high resolution and anincrease in transmittance caused by securing of the transmissive area.

Therefore, the inventors has invented a transparent display device whichrealizes a high resolution, has a transmittance of 50% or more in atransparent mode, and changes a color at a high speed.

The above-described background is possessed by the inventor of theapplication for deriving the invention, or is technology informationthat has been acquired in deriving the invention. The above-describedbackground is not necessarily known technology disclosed to the generalpublic before the application of the invention.

SUMMARY

Accordingly, the present invention is directed to provide a transparentdisplay device that substantially obviates one or more problems due tolimitations and disadvantages of the related art.

An aspect of the present invention is directed to provide a transparentdisplay device which realizes a high resolution in a display mode.

Another aspect of the present invention is directed to provide atransparent display device which realizes a transmittance of 50% or morein a transparent mode.

Additional advantages and features of the invention will be set forth inpart in the description which follows and in part will become apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from practice of the invention. Theobjectives and other advantages of the invention may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the invention, as embodied and broadly described herein, there isprovided a transparent display device that includes a first substrateand a second substrate facing each other, a thin film transistor (TFT)disposed on one surface of the first substrate, a first transparentelectrode connected to the TFT, a second transparent electrode disposedon the second substrate to face the first substrate, and anelectrochromic element provided between the first transparent electrodeand the second transparent electrode.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 is a plan view of a related art transparent display device;

FIG. 2 is a cross-sectional view of a transparent display deviceaccording to an embodiment of the present invention;

FIG. 3 is a plan view of a pixel operation of a transparent displaydevice according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view of a transparent display deviceaccording to another embodiment of the present invention;

FIG. 5 is an expanded view of area A of the transparent display deviceillustrated in FIG. 4;

FIG. 6 is an expanded view of area B of the transparent display deviceillustrated in FIG. 4; and

FIG. 7 is an expanded view of area C of the transparent display deviceillustrated in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Advantages and features of the present invention, and implementationmethods thereof will be clarified through following embodimentsdescribed with reference to the accompanying drawings. The presentinvention may, however, be embodied in different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the present invention tothose skilled in the art. Further, the present invention is only definedby scopes of claims.

A shape, a size, a ratio, an angle, and a number disclosed in thedrawings for describing embodiments of the present invention are merelyan example, and thus, the present invention is not limited to theillustrated details. Like reference numerals refer to like elementsthroughout. In the following description, when the detailed descriptionof the relevant known function or configuration is determined tounnecessarily obscure the important point of the present invention, thedetailed description will be omitted. In a case where ‘comprise’,‘have’, and ‘include’ described in the present specification are used,another part may be added unless ‘only˜’ is used. The terms of asingular form may include plural forms unless referred to the contrary.

In construing an element, the element is construed as including an errorrange although there is no explicit description.

In describing a position relationship, for example, when a positionrelation between two parts is described as ‘on˜’, ‘over˜’, ‘under˜’, and‘next˜’, one or more other parts may be disposed between the two partsunless ‘just’ or ‘direct’ is used.

In describing a time relationship, for example, when the temporal orderis described as ‘after˜’, ‘subsequent˜’, ‘next˜’, and ‘before˜’, a casewhich is not continuous may be included unless ‘just’ or ‘direct’ isused.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention.

Features of various embodiments of the present invention may bepartially or overall coupled to or combined with each other, and may bevariously inter-operated with each other and driven technically as thoseskilled in the art can sufficiently understand. The embodiments of thepresent invention may be carried out independently from each other, ormay be carried out together in co-dependent relationship.

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

FIG. 2 is a diagram illustrating a transparent display device 100according to an embodiment of the present invention.

Referring to FIG. 2, the transparent display device 100 according to anembodiment of the present invention may include a first substrate 110and a second substrate 210.

The first substrate 110 may include a thin film transistor (TFT) 120, apassivation layer 130, a first transparent electrode 140, a separationwall 150, and an electrochromic layer 160. The second substrate 210 mayinclude a second transparent electrode 220 and a counter layer 230.Also, an electrolyte layer 190 may be disposed between the firstsubstrate 110 and the second substrate 210. The electrochromic layer160, the electrolyte layer 190, and the counter layer 230 may each bedefined as an electrochromic element.

The first substrate 110 and the second substrate 210 may each be atransparent material or a plastic film. For example, each of the firstsubstrate 110 and the second substrate 210 may be a sheet or a filmwhich includes cellulose resin such as triacetyl cellulose (TAC),diacetyl cellulose (DAC), or the like, cyclo olefin polymer (COP) suchas orbornene derivatives or the like, acrylic resin such as cyclo olefincopolymer (COC), poly(methylmethacrylate) (PMMA), or the like,polyolefin such as polycarbonate (PC), polyethylene (PE), polypropylene(PP), or the like, polyester such as polyvinyl alcohol (PVA), poly ethersulfone (PES), polyetheretherketone (PEEK), polyetherimide (PEI),polyethylenenaphthalate (PEN), polyethyleneterephthalate (PET), or thelike, polyimide (PI), polysulfone (PSF), fluoride resin, and/or thelike, but is not limited thereto.

The TFT 120 may include a gate electrode 121, a gate insulation layer122, a semiconductor layer 123, an ohmic layer 124, a source electrode125, and a drain electrode 126.

A metal material may be deposited on the first substrate 110, and aphotoresist may be deposited on the metal material. Subsequently, a maskprocess where an exposure process, a development process, and an etchingprocess are sequentially performed may be performed by using a mask (notshown), thereby forming the gate electrode 121.

Moreover, although not shown, a gate line connected to the gateelectrode 121 may be formed simultaneously in the process of forming thegate electrode 121. Here, the gate electrode 121 may be formed bydepositing one metal material, or may be formed by depositing two metalmaterials.

The gate insulation layer 122 may be disposed on a top of the firstsubstrate 110 and may cover one surface of the gate electrode 121. Here,the gate insulation layer 122 may be formed through a plasma enhancedchemical vapor deposition (PECVD) process.

The semiconductor layer 123 may include amorphous silicon (a-Si) orcrystalline silicon. The ohmic layer 124 included in the TFT 120 may beformed by adding P-type or N-type impurities into the amorphous siliconor the crystalline silicon. The semiconductor layer 123 may beohmic-contacted with the source electrode 125 and the drain electrode126 by the ohmic layer 124, thereby enhancing characteristic of the TFT120.

The source electrode 125 and the drain electrode 126 included in the TFT120 may be formed by following process. An electrode material isdeposited on the semiconductor layer 123 and the electrode material isetched with a mask, thus the source electrode 125 and the drainelectrode 126 may be formed.

The source electrode 125 may be electrically connected to thebelow-described first transparent electrode 140 through a contact hole.Accordingly, an image may be realized by transferring an electricalsignal to the below-described electrochromic element.

The passivation layer 130 may be formed on the TFT 120, and in moredetail, may be formed on a top of each of the source electrode 125 andthe drain electrode 126. The passivation layer 130 protects the TFT 120.The passivation layer 130 may include an inorganic insulating material,for example, silicon oxide (SiO_(x)) or silicon nitride (SiN_(x)), butis not limited thereto. The passivation layer 130 may extend to thebelow-described electrochromic element.

The first transparent electrode 140 may be formed on a top of thepassivation layer 130 and may be electrically connected to the sourceelectrode 125. The passivation layer 130 may include a contact hole, andthus a voltage may be applied to the first transparent electrode 140.The first transparent electrode 140 may include silver oxide (forexample, AgO, Ag₂O, or Ag₂O₃), aluminum oxide (for example, Al₂O₃),tungsten oxide (for example, WO₂, WO₃, or W₂O₃), magnesium oxide (forexample, MgO), molybdenum oxide (for example, MoO₃), zinc oxide (forexample, ZnO), tin oxide (for example, SnO₂), indium oxide (for example,In₂O₃), chromium oxide (for example, CrO₃ or Cr₂O₃), antimony oxide (forexample, Sb₂O₃ or Sb₂O₅), titanium oxide (for example, TiO₂), nickeloxide (for example, NiO), copper oxide (for example, CuO or Cu₂O),vanadium oxide (for example, V₂O₃ or V₂O₅), cobalt oxide (for example,CoO), iron oxide (for example, Fe₂O₃ or Fe₃O₄), niobium oxide (forexample, Nb2O5), indium tin oxide (for example, ITO), indium zinc oxide(for example, IZO), aluminum-doped zinc oxide (for example, ZAO),aluminum-doped tin oxide (for example, TAO), or antimony tin oxide (forexample, ATO), but is not limited thereto.

The separation wall 150 may be disposed between the first transparentelectrode 140 and the second transparent electrode 220 and may define apixel of the transparent display device 100 according to an embodimentof the present invention. That is, the separation wall 150 may bedisposed between adjacent pixels among a red pixel, a green pixel, and ablue pixel and may prevent mixing of the electrolyte layer 190. Also,the separation wall 190 may maintain a certain gap between the firstsubstrate 110 and the second substrate 210.

The electrochromic layer 160 and the counter layer 230 may be formedover a top of the separation wall 150 as shown in FIG. 2, but is notlimited thereto. For example, the electrochromic layer 160 may not beformed over the top of the separation wall 150 so that the separationwall 150 contacts the counter layer 230. Alternatively, theelectrochromic layer 160 and the counter layer 230 may not be formedover the top of the separation wall 150 so that the separation wall 150contacts the second transparent electrode 220.

The separation wall 150 may be formed of a transparent material. In thiscase, the separation wall 150 may be formed of one of photoresist,ultraviolet (UV)-curable polymer, and polydimethylsiloxane, but is notlimited thereto.

The separation wall 150 may be narrowed in a direction from theelectrochromic layer 160 to the counter layer 230, but is not limitedthereto. For example, a width of the separation wall 150 may beconstant, or may be narrowed progressively closer to the electrochromiclayer 160.

A plan view of the separation wall 150 is not shown, but the separationwall 150 may have various shapes in the plan view thereof. For example,the separation wall 150 may have a stripe shape, a dot shape, ahoneycomb shape, and/or the like, but is not limited thereto.

The electrochromic layer 160 may include an electrochromic material.When a reduction reaction is performed on the electrochromic material,the electrochromic material may absorb a certain color to have thecertain color, and when an oxidation reaction is performed on theelectrochromic material, the electrochromic material may be changed to atransparent material. For example, the electrochromic material accordingto an embodiment of the present invention may include a compoundrepresented by the following Formula 1.

where R₁ to R₁₀ may be individually selected from hydrogen and asubstituted or unsubstituted hydrocarbon. The hydrocarbon may beselected from the group consisting of an alkyl group, a cycloalkylgroup, a polycycloalkyl group, a heterocycloalkyl group, an aryl group,an aralkyl group, an alkoxy group, an alkenyl group, and an alkynylgroup. The hydrocarbon may be substituted by a group selected from aryl,halogens, nitrogen, oxygen, alcohols, esters, ammonium salts, orphosphonium salts.

As described above, the electrochromic layer 160 may realize atransparent mode where when a voltage is not applied to the firsttransparent electrode 140, an oxidation reaction is performed on thematerial of Formula 1, and thus, the material is changed to atransparent material. Also, when the voltage is applied to the firsttransparent electrode 140, a reduction reaction is performed on thematerial of Formula 1, and thus, the electrochromic layer 160 may have acertain color. In this case, the electrochromic layer 160 may have acertain color such as red, green, blue, or the like, based on asubstituted material in R₁ to R₁₀ of Formula 1.

For example, the electrochromic layer 160 may include a compoundrepresented by the following Formula 2 where the R₂ of Formula 1 is amethyl group, and the other R groups are hydrogen atoms. When a voltageis applied to the first transparent electrode 140, a reduction reactionmay be performed on a material of the following Formula 2 to realizered.

For example, the electrochromic layer 160 may include a compoundrepresented by the following Formula 3 where the R₂ and R₇ of Formula 1are each a pentyl group, and the other R groups are hydrogen atoms. Whenthe voltage is applied to the first transparent electrode 140, areduction reaction may be performed on a material of the followingFormula 3 to realize green.

For example, the electrochromic layer 160 may include a compoundrepresented by the following Formula 4 where the R₂ and R₇ of Formula 1are each a phenyl group, and the other R groups are hydrogen atoms. Whenthe voltage is applied to the first transparent electrode 140, areduction reaction may be performed on a material of the followingFormula 4 to realize blue.

As described above, when the voltage is applied to the first transparentelectrode 140, a reduction reaction may be performed on a materialrepresented by each of Formulas 2 to 4, and thus, the electrochromiclayer 160 may have a certain color. However, the present embodiment isnot limited thereto. In other embodiments, the electrochromic layer 160may include an electrochromic material for realizing a color other thanred, green, and blue.

The electrolyte layer 190 may include an electrolyte, a polymer, and aUV initiator. The electrolyte may be, for example, lithium perchlorate,t-butylammoinum perchlorate, t-butylammoinum-t-fluoroborate,tetrabutylammonium trifluoromethanesulfonate, or the like. The polymermay be, for example, a polyacrylate-based polymer, a polyester-basedpolymer, an epoxy-based polymer, or the like. The UV initiator may be,for example, benzoinethers, amines, or the like. The electrolyte layer190 may supply a positive ion and a negative ion in order for theelectrochromic layer 160 and the counter layer 230 to perform anoxidation-reduction reaction.

The second transparent electrode 220 on the second substrate 210 may beformed all over the second substrate 210 and may include a materialwhich is the same as that of the first transparent electrode 140. Thesecond transparent electrode 210 may include silver oxide (for example,AgO, Ag₂O, or Ag₂O₃), aluminum oxide (for example, Al₂O₃), tungstenoxide (for example, WO₂, WO₃, or W₂O₃), magnesium oxide (for example,MgO), molybdenum oxide (for example, MoO₃), zinc oxide (for example,ZnO), tin oxide (for example, SnO₂), indium oxide (for example, In₂O₃),chromium oxide (for example, CrO₃ or Cr₂O₃), antimony oxide (forexample, Sb₂O₃ or Sb₂O₅), titanium oxide (for example, TiO₂), nickeloxide (for example, NiO), copper oxide (for example, CuO or Cu₂O),vanadium oxide (for example, V₂O₃ or V₂O₅), cobalt oxide (for example,CoO), iron oxide (for example, Fe₂O₃ or Fe₃O₄), niobium oxide (forexample, Nb₂O₅), indium tin oxide (for example, ITO), indium zinc oxide(for example, IZO), aluminum-doped zinc oxide (for example, ZAO),aluminum-doped tin oxide (for example, TAO), or antimony tin oxide (forexample, ATO), but is not limited thereto.

The counter layer 230 may be provided on one surface of the secondtransparent electrode 220 to face the first substrate 110. The counterlayer 230 may be a layer that helps an oxidation-reduction reaction tobe smoothly performed on the electrochromic layer 160. When an oxidationreaction is performed on the counter layer 230, the counter layer 230may absorb a certain color to have a certain color. Also, the counterlayer 230 may include a counter material which is changed to atransparent material by the reduction reaction. However, the counterlayer 230 may be omitted. Also, the counter layer 230 may include acompound represented by the following Formula 5.

where X may be —NR₁₀—, —O—, or —S—, and R₁ to R₁₀ may be individuallyselected from hydrogen and a substituted or unsubstituted hydrocarbon.The hydrocarbon may be selected from the group consisting of an alkylgroup, a cycloalkyl group, a polycycloalkyl group, a heterocycloalkylgroup, an aryl group, an aralkyl group, an alkoxy group, an alkenylgroup, and an alkynyl group. The hydrocarbon may be substituted by agroup selected from aryl, halogens, nitrogen, oxygen, alcohols, esters,ammonium salts, or phosphonium salts.

The counter layer 230 and the electrochromic layer 160 may have thefollowing relationship. If an oxidation reaction is performed on thecounter layer 230, a reduction reaction may be performed on theelectrochromic layer 160, and if a reduction reaction is performed onthe counter layer 230, an oxidation reaction may be performed on theelectrochromic layer 160.

FIG. 3 is a diagram illustrating a pixel operation of the transparentdisplay device 100 according to an embodiment of the present invention.

Referring to FIG. 3, the transparent display device 100 according to anembodiment of the present invention may operate in a transparent modeand a display mode.

That is, when a voltage is applied to the first transparent electrode140 and the second transparent electrode 220, an electrochemicaloxidation-reduction reaction may be performed on the counter layer 230and the electrochromic layer 160, and thus, a color of each of thecounter layer 230 and the electrochromic layer 160 may be changed.

For example, when a positive voltage is applied to the first transparentelectrode 140 and a negative voltage is applied to the secondtransparent electrode 220, a reduction reaction may be performed on theelectrochromic layer 160, and an oxidation reaction may be performed onthe counter layer 230. In this manner, the electrochromic layer 160 mayhave a certain color due to the reduction reaction, thereby realizingthe display mode where an image is displayed.

Moreover, when a negative voltage is applied to the first transparentelectrode 140 and a positive voltage is applied to the secondtransparent electrode 220, a reduction reaction may be performed on thecounter layer 230, and an oxidation reaction may be performed on theelectrochromic layer 160. In this manner, the electrochromic layer 160may be transparently changed by the oxidation reaction, therebyrealizing the transparent mode.

In the transparent display device 100 according to an embodiment of thepresent invention, when an image is displayed in the display mode, atransmittance may be controlled by adjusting a driving voltage. That is,the display mode where an image is displayed and the transparent modewhere an object located on a backside is shown without an image beingdisplayed may be performed simultaneously. Also, in a state where avoltage is not applied, the transparent display device 100 may have atransmittance of about 70% to about 90% and an image color change speedof 100 m/sec or less. That is, in the transparent display device 100according to an embodiment of the present invention, since a polarizingfilm is removed unlike the related art transparent display device, ahigher transmittance is realized, and a transparent area wider than aTFT area is secured for each pixel. Accordingly, in the transparentdisplay device 100 according to an embodiment of the present invention,a high transmittance is secured in the transparent mode.

FIG. 4 is a diagram illustrating a transparent display device 100according to another embodiment of the present invention. FIG. 5 is adiagram illustrating an area A illustrated in FIG. 4. FIG. 6 is adiagram illustrating an area B illustrated in FIG. 4. FIG. 7 is adiagram illustrating an area C illustrated in FIG. 4.

The transparent display device 100 of FIG. 4 has been implemented bymodifying some elements of the transparent display device 100illustrated in FIGS. 2 and 3, and thus, descriptions of repetitiveelements are not repeated.

Referring to FIG. 4, in the transparent display device 100 according toanother embodiment of the present invention, a core material 170 such astransparent conductive oxide (TCO) or the like and an electrochromicmaterial 180 combined with the core material 170 may be included in anelectrochromic layer 160 and a counter layer 230. The core material 170may be a material which is obtained by surface-treating TiO₂ on TiO₂,In₂O₃, SnO₂, RuO₂, or ITO.

Referring to FIGS. 5 to 7, the core material 170 may be provided on onesurface of each of first and second transparent electrodes 140 and 220and a passivation layer 130. The core material 170 may be in the form ofspherical particles. The electrochromic material 180 may cling tosurfaces of the spherical particles. The core material 170 isillustrated as configuring two layers in the drawing, but this is forconvenience of description. The present embodiment is not limitedthereto.

The electrochromic material 180 clinging to a surface of the corematerial 170 may include the above-described materials of Formulas 1 to5. Further, the electrochromic layer 160 may include the materials ofFormulas 1 to 4, and the counter layer 230 may include the material ofFormula 5.

In detail, the core material 170 may be defined by the functional groupsR₁ to R₁₀ represented in Formulas 1 to 5, and the electrochromicmaterial 180 may be a viologen (a salt including two pyridinyl groups)represented in Formulas 1 to 4.

In addition to the features of the transparent display device 100according to an embodiment of the present invention, the transparentdisplay device 100 according to another embodiment of the presentinvention has a feature where since the electrochromic material 180clinging to the surface of the core material 170 and thus is changed incolor, a time taken in changing a color through diffusion is reduced,and thus, a color is changed at a super-high speed.

As described above, according to the embodiments of the presentinvention, provided is a transparent display device which realizes ahigh resolution when displaying an image in the display mode.

Moreover, according to the embodiments of the present invention,provided is a transparent display device which realizes a transmittanceof 50% or more in a transparent mode.

Moreover, according to the embodiments of the present invention,provided is a transparent display device which changes a color at a highspeed when displaying an image in the display mode.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1.-16. (canceled)
 17. A transparent display device which operates in atransparent mode and a display mode, comprising: a first substrate and asecond substrate facing each other; a first transparent electrodedisposed on one surface of the first substrate; a second transparentelectrode disposed on the second substrate to face the first substrate;and an electrochromic element provided between the first transparentelectrode and the second transparent electrode.
 18. The transparentdisplay device of claim 17, wherein the electrochromic element has acolor in the display mode and is transparently changed in thetransparent mode.
 19. The transparent display device of claim 18,wherein the electrochromic element has a transmittance of 50% or more inthe transparent mode.
 20. The transparent display device of claim 17,further comprising: a thin film transistor (TFT) disposed between thefirst substrate and the first transparent electrode, the TFT comprises asource electrode and a passivation layer disposed on the sourceelectrode, and the source electrode transfers an electrical signal tothe first transparent electrode through a contact hole included in thepassivation layer.
 21. The transparent display device of claim 17,wherein the electrochromic element comprises: an electrochromic layerprovided on the first transparent electrode; a counter layer provided onthe second transparent electrode to face the first substrate; and anelectrolyte layer disposed between the electrochromic layer and thecounter layer.
 22. The transparent display device of claim 21, whereinthe electrochromic layer includes an electrochromic material forrealizing one of red, green and blue in the display mode.
 23. Thetransparent display device of claim 22, wherein the electrochromicmaterial comprises a compound represented by Formula 1:

wherein R₁ to R₁₀ is individually selected from hydrogen and asubstituted or unsubstituted hydrocarbon, and wherein the hydrocarbon isselected from the group consisting of an alkyl group, a cycloalkylgroup, a polycycloalkyl group, a heterocycloalkyl group, an aryl group,an aralkyl group, an alkoxy group, an alkenyl group, and an alkynylgroup.
 24. The transparent display device of claim 23, wherein thehydrocarbon is substituted by a group selected from aryl groups,halogen, nitrogen, oxygen, alcohols, esters, ammonium salts, orphosphonium salts.
 25. The transparent display device of claim 22,wherein the electrochromic material comprises a compound represented byFormula 2:


26. The transparent display device of claim 22, wherein theelectrochromic material comprises a compound represented by Formula 3:


27. The transparent display device of claim 22, wherein theelectrochromic material comprises a compound represented by Formula 4:


28. The transparent display device of claim 21, wherein theelectrochromic layer is oxidized, and the counter layer is reduced inthe transparent mode.
 29. The transparent display device of claim 21,wherein the electrochromic layer is reduced to produce a color, and thecounter layer is oxidized in the display mode.
 30. The transparentdisplay device of claim 21, wherein the counter layer comprises acompound represented by Formula 5:

wherein X is selected from —NR₁₀—, —O— and —S—, and R₁ to R₁₀ isindividually selected from hydrogen and a substituted or unsubstitutedhydrocarbon, and wherein the hydrocarbon is selected from the groupconsisting of an alkyl group, a cycloalkyl group, a polycycloalkylgroup, a heterocycloalkyl group, an aryl group, an aralkyl group, analkoxy group, an alkenyl group, and an alkynyl group.
 31. Thetransparent display device of claim 30, wherein the hydrocarbon issubstituted by a group selected from aryl groups, halogens, nitrogen,oxygen, alcohols, esters, ammonium salts, or phosphonium salts.
 32. Thetransparent display device of claim 17, further comprising a separationwall dividing a red pixel area, a green pixel area, and a blue pixelarea.
 33. The transparent display device of claim 17, wherein: when avoltage is not applied, the transparent display device has atransmittance of about 70% to about 90%.
 34. The transparent displaydevice of claim 17, wherein: when a voltage is not applied, thetransparent display device has an image color change speed of 100 m/secor less.